Severe Leaf Spot Disease Research Articles

Effect of woodchips mulch on performance of eight blackcurrant cultivars

Blackcurrant is one of the main berry crops grown in Latvia. Local climatic conditions and market demands require an accurate choice of well-adapted cultivars and improving of growing technologies in order to obtain higher yield and reduce production costs. This study presents the evaluation results of eight blackcurrant cultivars: ‘Bagira’, ‘Ben Connan’, ‘Ben Tirran’, ‘Chereshneva’, ‘Lentyai’, ‘Mara Eglite’, ‘Veloi’ and Titania’ in two growing practices – with application of woodchips mulch (using increased N fertilization rate) and without mulching. The trial was established in 2010 at Pūre Horticultural Research Centre, Latvia. Plant vegetative growth, phenological parameters, winter hardiness, yield, fruit quality, incidence of pests and diseases were evaluated during 2012-2016. All evaluated cultivars showed good adaptability for growing in local conditions. Mulching of soil with woodchips did not influence blackcurrant phenological development, productivity, fruit size and damage severity by pests, whereas it reduced weeds growth and leaf spot disease severity.

First Report of Alternaria alternata Causing Leaf Spot of Senecio cannabifolius in China

HomePlant DiseaseVol. 103, No. 5First Report of Alternaria alternata Causing Leaf Spot of Senecio cannabifolius in China PreviousNext DISEASE NOTES OPENOpen Access licenseFirst Report of Alternaria alternata Causing Leaf Spot of Senecio cannabifolius in ChinaS. Chen, D. Yang, L. Yang, and H. YuanS. Chenhttp://orcid.org/0000-0002-4628-370XKey Laboratory of Integrated Pest Management in Crops, Ministry of Agriculture, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing 100193, ChinaSearch for more papers by this author, D. YangKey Laboratory of Integrated Pest Management in Crops, Ministry of Agriculture, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing 100193, ChinaSearch for more papers by this author, L. YangKey Laboratory of Integrated Pest Management in Crops, Ministry of Agriculture, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing 100193, ChinaSearch for more papers by this author, and H. Yuan†Corresponding author: H. Yuan; E-mail Address: hzhyuan@ippcaas.cnKey Laboratory of Integrated Pest Management in Crops, Ministry of Agriculture, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing 100193, ChinaSearch for more papers by this authorAffiliationsAuthors and Affiliations S. Chen D. Yang L. Yang H. Yuan † Key Laboratory of Integrated Pest Management in Crops, Ministry of Agriculture, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing 100193, China Published Online:12 Mar 2019https://doi.org/10.1094/PDIS-08-18-1341-PDNAboutSections ToolsAdd to favoritesDownload CitationsTrack Citations ShareShare onFacebookTwitterLinked InRedditEmailWechat Senecio cannabifolius Less. is a perennial herb belongs to the family Compositae. The plant has been widely used as a folk traditional medicine for the treatment of inflammation, pneumonia, bronchitis, and viral respiratory tract infection (Chen et al. 2015; Yan and Li 1997). In summer 2018, severe leaf spot disease was observed in Chahaer city, Inner Mongolia, China. At the beginning of June, the bottom leaves were the first to become infected. Symptoms on leaves initially appeared as small circular, dark brown, necrotic spots. Then, they gradually enlarged in size, becoming irregular. Later, severe infections were seen as coalesced lesions and blighted leaves and stems. Yield losses as much as 80% were reported on approximately 1,000 acres in various S. cannabifolius growing regions. Leaf tissues (5 × 5 mm), cut from the margins of lesions, were surface disinfected by 1% NaClO for 1 min, placed on potato dextrose agar, and incubated at 25°C with a 12-h photoperiod. Fungus Alternaria alternata was consistently isolated and preliminarily identified on the basis of morphological characteristics. Dark brown conidia produced in long chains by conidiophores. Conidia had short beaks and ranged from 15.86 to 33.62 × 12.67 to 18.39 μm and had three to six transverse and zero to three longitudinal septa (n = 60). To confirm the identification, DNA from five single-spore isolates was extracted, and ITS1-5.8-ITS2, the endopolygalacturonase (endoPG), and Alternaria major allergen (Alta1) genes were amplified and further sequenced using primers ITS1/ITS4, PG3/PG2b (Andrew et al. 2009), and Alt-for/Alt-rev (Woudenberg et al. 2015), respectively. A GenBank BLAST search showed 99 to 100% identity to the type species A. alternata (accession nos. MG025876 for ITS1-5.8-ITS2, AY295030 for endoPG, and KP123956 for Alta1) for all isolates, and sequence data were submitted to GenBank (accession nos. MH728994 [ITS1-5.8-ITS2], MH728996 [endoPG], and MH728995 [Alta1]). Pathogenicity tests were conducted to confirm Koch’s postulates, by spraying leaves of 10 healthy, 3-month-old potted S. cannabifolius plants with a spore suspension of 106 conidia/ml. A. alternata spores were suspended in 0.1% Tween 80 and sprayed onto leaves until runoff. Control plants were sprayed with a sterile 0.1% Tween 80 mixture until runoff. Plants were covered by polyethylene bags for 3 days to achieve high humidity levels and incubated in a greenhouse at 25°C. After 3 days, spots similar to those observed in the field appeared on the leaves of inoculated plants, whereas control plants remained symptomless. Isolations made from diseased spots consistently yielded A. alternata. The pathogenicity test was repeated twice under the same conditions. To our knowledge, this is the first report of A. alternata causing leaf spot on S. cannabifolius. A. alternata has also been reported infecting other Senecio genus plants, for example, S. cineraria in Germany and S. skirrhodon in New Zealand (Woudenberg et al. 2015). Other than Senecio, A. alternata has a wide host range of more than 700 documented plant species (https://nt.ars-grin.gov/fungaldatabases/). Future research will focus primarily on management of this disease.

Evaluation of Fungicide for the Management of Leaf and Fruit Spot (Phaeoramularia angolensis) of Sweet Orange in West & Kellem Wollaga Zones

Sweet orange (Citrus sinensis) is an important fruit crop in the daily diet, good source of food nutrients, cash to the farmers. The leaf and fruit spot disease caused by Phaeoramularia angolensis is one of the most devastating airborne diseases and also the main constraints contributing to the low productivity of citrus plantation in 20 African countries including Ethiopia. The experiment was conducted to evaluate three fungicide (Unizeb 80% WP, Trust-cymocop 439.5 WP, and Benomyl 500 WP) and combination of the two each fungicide under field conditions for the management of leaf and fruit spot disease and also to assess the yield losses. Not significant different in disease incidence between treatments and there was a significant difference in the leaf and fruit spot disease severity and Area under Disease Progressive Curve (AUDPC) among treatments. On the final date of disease assessment, among the fungicide, Unizeb sprayed was recorded the lowest disease severity (17.33%) and (18.17%), whereas the highest disease severity of (46.67%) and (45.83 %) were recorded on leaf and fruit spot on control plots, respectively. The highest fruit yield of 6.14 and 5.94 t/ha were also recorded from plots sprayed with Unizeb 80% WP and Benomyl 500 WP fungicide. Unizeb 80% WP fungicide applied exhibited maximum partial cost net benefit from all plots that means the highest (123970.00 ETB ha -1 ) was recorded and followed by Benomyl 500 WP (111520.00 ETB ha -1 ) fungicide treated plots. The results of the present study revealed that the novel possibility of using Unizeb foliar spray with four times which was found to be an effective in decreasing leaf and fruit spot disease symptoms on sweet orange in Kellem Wollega, Western Oromiya and increased yield. Keywords: Sweet Orange, Leaf and Fruit spot disease, Fungicides, Yield and Cost benefit. DOI : 10.7176/JBAH/9-5-01 Publication date :March 31 st 2019

Rapid Inoculation Technique and Biological Control of Leaf Spot Disease in Oil Palm

Oil palm (Elaeis guineensis) is one of the most efficient oil-producing crops in the world. However, fungal diseases such as basal stem rot (BSR) caused by Ganoderma sp. causes significant loss to the yield of adult palms. Apart from BSR, leaf spot disease caused by Curvularia sp. also causes significant loss during nursery stages. In this study, Curvularia sp. was isolated from a diseased palm seedling and a rapid and reproducible artificial inoculation method was developed. The technique has bioassay to determine the level of success of the control of leaf spot disease in a glasshouse setting. A natural, organic cyclic peptide fungicide and living cells of a bacterial strain Paraburkholderia sp. CP01 were tested for their efficacy to control leaf spot in oil palm seedlings. The severity of leaf spot disease in oil palm seedlings treated by organic cyclic peptide fungicide and CP01 was significantly lower than untreated control, indicating potential biological control agents. The results presented here provide technical reference and novel approach to controlling leaf spot disease of oil palm.

Spatial Organisation Influences Citrus <i>Pseudocercospora</i> Leaf and Fruit Spot Disease Severity in Cocoa-Based Agroforestry Systems

An investigation to assess the spatial structure and severity of Pseudocercospora leaf and fruit spot disease (PLFSD) on citrus trees in cocoa-based agroforests was carried out in three contrasting ecological zones in southern Cameroon, viz: 1) the humid forest zone, 2) the degraded forest zone, and 3) the forest-savannah transition zone. Two main parameters were investigated viz: 1) the spatial structure of cocoa based agroforests, and 2) the disease severity. In total, the spatial structure of 19 cocoa-based agroforests was analysed using the Ripley K(r) function, meanwhile the collection of epidemiological data that consisted of noting the presence of PLFSD spots on leaves and fruits on 438 citrus trees was used to characterise the severity of the disease. Results showed that, the spatial structure of citrus trees in these agroforests investigated were regular in seven plots, random in nine, and aggregated in three. Aggregated plots presented a significantly higher mean of disease severity on leaves and fruits (28.55 and 30.37 respectively), as compared to randomised (20.91 and 16.32 respectively) and regular plots (16.28 and 14.97 respectively), at P-value

Effects of zinc oxide nanoparticles (ZnO NPs) and some plant pathogens on the growth and nodulation of lentil (Lens culinaris Medik.)

Effects of ZnO nanoparticles (NPs) were studied on lentil plants inoculated with Alternaria alternata, Fusarium oxysporum f. sp. lentis, Xanthomonas axonopodis pv. phaseoli, Pseudomonas syringae pv. syringae and Meloidogyne incognita. Plant growth, chlorophyll, carotenoid contents, nitrate reductase (NR) activity and nodulation of lentil both in the presence and absence of Rhizobium sp. were examined in a pot test. Inoculation of plants with A. alternata / F. oxysporum f. sp. lentis / X. axonopodis pv. phaseoli / P. syringae pv. syringae or M. incognita caused a significant reduction in plant growth, number of pods per plant, chlorophyll, carotenoids and NR activity over uninoculated control. Inoculation of plants with Rhizobium sp. with or without pathogen increased plant growth and number of pods per plant, chlorophyll, carotenoids and NR activity. When plants were grown without Rhizobium, a foliar spray of plants with 10 ml solution of 0.1 mg ml–1of ZnO NPs per plant caused a significant increase in plant growth and number of pods, chlorophyll, carotenoid contents and NR activity in both inoculated and uninoculated plants. Spray of ZnO NPs to plants inoculated with Rhizobium sp. caused non significant increase in plant growth, number of pods per plant, chlorophyll, carotenoid contents and NR activity when plants were either uninoculated or inoculated with pathogens. Numbers of nodules per root system were high in plants treated with Rhizobium sp. but foliar spray of ZnO NPs had adverse effect on nodulation. Inoculation of plants with test pathogens also reduced nodulation. Spray of ZnO NPs to plants reduced galling, nematode multiplication, wilt, blight and leaf spot disease severity indices.

Biological control of Pseudomonas syringae pv. aptata on sugar beet with Bacillus pumilus SS-10.7 and Bacillus amyloliquefaciens (SS-12.6 and SS-38.4) strains.

Assessment of biological control of Pseudomonas syringae pv. aptata using crude lipopeptide extracts (CLEs) of two Bacillus amyloliquefaciens strains (SS-12.6 and SS-38.4) and one Bacillus pumilus strain (SS-10.7). The minimum inhibitory concentration (MIC) of CLEs and their combinations against the pathogen and potential interaction between the extracts were determined invitro. The most effective antibacterial activity was achieved with the CLE from B. amyloliquefaciens SS-12.6, with an MIC value of 0·63mgml-1 . Interactions between CLE combinations were mostly indifferent. The biocontrol potential of CLEs, mixtures of CLEs, and cell culture of B. amyloliquefaciens SS-12.6 was tested on sugar beet plants inoculated with P. syringae pv. aptata P53. The best result in inhibiting the appearance of tissue necrosis (up to 92%) was achieved with B. amyloliquefaciens SS-12.6 cell culture. This work demonstrated significant biocontrol potential of the CLE and cell culture of B. amyloliquefaciens SS-12.6 which successfully suppress leaf spot disease severity on sugar beet plants. The findings of biocontrol of sugar beet emerging pathogen will contribute to growers in terms of alternative disease control management. This study represents first assessment of biological control of P. syringae pv. aptata.

Effect of different levels of nitrogen and potassium against leaf spots disease of groundnut in different fertility gradient soil in field

The occurrence of early and late leaf spots of groundnut under influence of variable soil fertility states with further interaction to different levels of nitrogen and potassium was measured and the same was correlated with the yield attributing parameters. Two different nitrogen and potassium combinations (20; 40 kg ha-1) applied on four different fertility gradient soil (low ,S1; medium ,S2 ; moderate ,S3 and high ,S4) showed minimum leaf spot disease severity and maximum diseases reduction in (S1) N40K20 (AUDPC 34.48 and 16.06% reduction); (S2) N40K40 (AUDPC- 32.88 and 13.68% reduction ); (S3) N20K40 (AUDPC 31.51 and 11.44% reduction) and (S4) N20K20 (AUDPC-25.40 and 11.58% reduction). The yield attributes like kernel number and weight per plant and kernel yield were also high in above combinations and fertility gradient soil. The linear regression value between disease severity and yield parameters showed a high co-relation regression and negatively significant at all fertility gradient soil and more responsive at low, medium and high fertility gradient soil irrespective of different N and K levels.

Morphology and Molecular Characterization of Alternaria argyranthemi on Chrysanthemum coronarium in China

Chrysanthemum coronarium is an economically important plant in Asia, and used medicinally, ornamentally and as a vegetable. In April 2017, leaf spot disease on C. coronarium was observed in Shiyan, Hubei, China. A single-spore isolate was obtained and identified based on morphology and sequence analysis using four regions (rDNA ITS, GAPDH, EF-1α, and RPB2). The results indicated that the fungus is Alternaria argyranthemi. The pathogenicity tests revealed that the species could cause severe leaf spot and blight disease on the host. This is the first report of leaf spot disease on C. coronarium caused by A. argyranthemi in the world, which is also a new record of Alternaria species in China.

Leaf and canopy reflectance spectrometry applied to the estimation of angular leaf spot disease severity of common bean crops.

This study is aimed at (i) estimating the angular leaf spot (ALS) disease severity in common beans crops in Brazil, caused by the fungus Pseudocercospora griseola, employing leaf and canopy spectral reflectance data, (ii) evaluating the informative spectral regions in the detection, and (iii) comparing the estimation accuracy when the reflectance or the first derivative reflectance (FDR) is employed. Three data sets of useful spectral reflectance measurements in the 440 to 850 nm range were employed; measurements were taken over the leaves and canopy of bean crops with different levels of disease. A system based in Principal Component Analysis (PCA) and Artificial Neural Networks (ANN) was developed to estimate the disease severity from leaf and canopy hyperspectral reflectance spectra. Levels of disease to be taken as true reference were determined from the proportion of the total leaf surface covered by necrotic lesions on RGB images. When estimating ALS disease severity in bean crops by using hyperspectral reflectance spectrometry, this study suggests that (i) successful estimations with coefficients of determination up to 0.87 can be achieved if the spectra is acquired by the spectroradiometer in contact with the leaves, (ii) unsuccessful estimations are obtained when the spectra are acquired by the spectroradiometer from one or more meters above the crop, (iii) the red to near-infrared spectral region (630–850 nm) offers the same precision in the estimation as the blue to near-infrared spectral region (440–850), and (iv) neither significant improvements nor significant detriments are achieved when the input data to the estimation processing system are the FDR spectra, instead of the reflectance spectra.

Identification and Characterization of Alternaria iridiaustralis Causing Leaf Spot on Iris ensata in China

In 2016, a severe leaf spot disease was found on Iris ensata Thumb. in Nanjing, China. The symptom was elliptical, fusiform, or irregularly necrotic lesion surrounded by a yellow halo, from which a small-spored Alternaria species was isolated. The fungus was identified as Alternaria iridiaustralis based on morphological characteristics. The pathogenicity tests revealed that the fungus was the causal pathogen of the disease. Phylogenic analyses using sequences of ITS, gpd, endoPG, and RPB2 genes confirmed the morphological identification. This study is the first report of A. iridiaustralis causing leaf spots on I. ensata in China.

Biosynthesis of nano Zinc and using of some nanoparticles in reducing of Cercospora leaf spot disease of sugar beet in the field

BIOSYNTHESIS of Zn nanoparticles(NPs) from 32 various plant samples were tested and subjected to 11 samples of ZnONPs from plant aqueous extracts, wherever, ZnNo3(1mmole) was used as precursor to synthesizing of ZnONPs. The UV-Vis spectral analysis of Morus nigra and Grevillea robusta plant leaves mix extracts (reaction mixture) were confirmed and showed performance of Zn NPs and exhibited as new sources for clean production and could be explored in various fields. During two tested seasons 2015/2016 and 2016/2017 and field conditions showed that, NPs of Ti followed by Zn caused to reducing of cercospora leaf spot (CLS) disease severity percentage of sugar beet plants and enhancement of TSS and sucrose contents, especially under high disease severity stress in season 2015/2016 compared to protected plants by eminent fungicide and control. NPs led to activation and recorded high enzymes activity values of enzymes of peroxidase up to 6 min and polyphenoloxidase up to 4 min estimation periods compared to control, so exhibited as mechanism in defense against CLS disease. Unseasonable weather conditions of temperature degrees, relative humidity percentage, wind velocity, pan evaporation and rain played an essential role in changement of CLS disease severity and susceptibility under field conditions during two tested seasons. The results recorded high percentages with first date of planting in September month in the first season of 2015/2016 with seven sugar beet genotypes than the second ones of October month and season of 2016/2017.

Effect of variety and apron star on incidence and severity of cercospora leaf spot disease of cowpea (Vigna unguiculata) in Sokoto, North-Western Nigeria

Field study was conducted during the 2015 raining season, at the Usmanu Danfodiyo University, Dry land farm, to evaluate the effect of Cercospora leaf spot disease and seed dressing chemical (Apron star) on different varieties of cowpea viz. Sampea-7, Sampea-8, Sampea-9, Sampea-11, Sampea-15 and Ex-Yumfa. Randomize Complete Block Design was used for the study. Results revealed that all the varieties were infected by Cercospora leaf spot disease at varying level. Ex-yumfa had highest disease incidence and severity both at 9 WAS and at harvest (40.385% and 55.128% incidence at 9 WAS and at harvest respectively) and (35.537% and 65.186% severity at 9was and at harvest). Lowest disease incidence was observed both at 9 WAS and at harvest on Sampea-15 (19.911% at 9 WAS and 28.884% incidence at harvest) and (11.911% and 21.852% severity) and no significant difference was recorded between dressed and undressed. Ex-Yumfa had lowest 100 grain (g) weight and yield per ha-1 while Sampea-7,8,9 and 11 are statistically similar also, there was no significant difference between dressed and undressed seeds in 100 grains weight seed and yield.

Efficiency of Some Biocides as Safe Alternatives to Fungicides on Cercospora Leaf Spot Control, their Effect on Biochemical Constituent and Yield of Sugar Beet

Cercospora leaf spot incited by Cercospora beticola Sacc. is a very detrimental fungal disease affecting sugar beet crop production in Egypt as well as sugar yield. The efficacy of four selected commercial biocides i.e., Biobac, Bio-Arc, Bio-Zeid and Plant Guard, was investigated to control Cercospora leaf spot on sugar beet plants in comparison with the recommended fungicide Score as a check difenoconazole fungicide as well as untreated control under field conditions at Sakha Agricultural Research Station, Kafr El-Sheikh Governorate, Egypt. The biocides and fungicide were sprayed at different three spray regimes as two sprays, four sprays or six sprays with 15 days intervals between sprays for such treatment. All tested biocides and Score fungicide led to significant decrease in Cercospora leaf spot disease severity of the treated sugar beet plants in comparison with control treatment. Increasing spraying numbers of the tested biocides or Score fungicide from two times to six sprays per season caused increasing reduction of Cercospora leaf spot severity. Spraying Plant guard, Bio-Zeid and Biobac biocides six times achieved very comparable effectiveness to Score treatment at the same spray regime in the two growing seasons 2015/2016 and 2016/2017, whereas, Bio-Arc was the less effective biocide treatment particularly when sprayed two times per season. All tested biocides at different spraying regimes led to significant increase in values of phenolic compounds, total chlorophyll, (achieved higher quality traits at the end of the season), sucrose (%) and purity (%) and top, root as well as sugar yield quality of sugar beet were significantly increased. The impurities of produced sugar as sodium, potassium and α-amino nitrogen in the juice were significantly decreased in comparison with untreated control during the two growing seasons. Overall results clarified that spraying Score fungicide or Bio- Zeid, Plant guard and Biobac, respectively six times resulted the highest increase of quality traits as sucrose (%) and purity %) and top, root and sugar yields of sugar beet and significant decrease in total amino acid, juice impurities (Na, K and α-a N %), whereas Bio- Arc when applied two times recorded the least effective treatment close to the control during the two growing seasons 2015/2016 and 2016/2017. It was concluded that biocides, Bio-Zeid, Plant guard and Biobac could be sprayed six times/season at 15 days intervals as alternatives to fungicide applications to control Cercospora leaf spot of sugar beet and to produce higher yields of root and sugar with better quality.

First Report of Alternaria alternata Causing Leaf Spot on Ipomoea purpurea in China

Ipomoea purpurea is widely used as an ornamental plant and in traditional Chinese medicine in China. Seed is used in treating edema and anuria, dispelling phlegm. In June 2016, severe leaf spot disease on I. purpurea with 30% disease incidence was observed in the Laoshan Mountain of Qingdao, China. Symptoms on leaves initially appeared as light to dark brown, necrotic spots with yellow borders or no borders. The spots gradually enlarged in size, becoming irregular. Tissue samples were taken from the margins of lesions, cut into small pieces, surface-disinfected with 70% ethanol for 30 seconds, rinsed with sterile water three times, placed on potato dextrose agar (PDA), and incubated at 25°C in the dark. A total of 10 isolates were obtained from 13 symptomatic leaf samples. Thereafter, 10 single spore isolates were obtained as described (Dong 2009) and transferred onto a potato carrot agar (PCA) medium (Mirkova 2003). After six days of growth on PCA at 25°C in the dark, colonies had round margins and aeria...

Keragaan Hama, Penyakit, dan Musuh Alami pada Budidaya Padi Organik

Organic rice cultivation intents to minimize the use of inorganic fertilizers and chemical pesticides, but in fact not apart from the disruption of pests and diseases. The study aimed to determine the pests, diseases, and natural enemies on organic rice cultivation. The research was conducted at Screen Field of ICRR at WS 2015/2016 and DS 2016, using Split Plot research design with three replications. The main plot was varieties of: 1). Inpari 25, 2). Inpari 33, and 3). Sintanur. The sub-plot was application of leaf extract of: 1). Mindi, 2). Soursop, 3). Mahogany, and 4). Control. Applications were performed on 4, 6, 8, and 10 weeks after planting (WAP). Observations of pests, diseases, and natural enemies on 5, 7, 9, and 11 WAP as many as 20 clumps/plots. The results showed that varieties and leaf extract applications significantly affected on severity of stem rot disease at 5 and 7 WAP in WS 2015/2016. In the rainy season found Yellowing on Inpari 25 and Inpari 33 varieties. However, Sintanur was more resistant to Yellowing with LCC value on two growing seasons was highest compared to the other varieties. Sintanur had the lowest Cercospora Leaf Spot disease severity compared to the other varieties. The severity of disease generally increased with the age of rice increase, while the pest population density and natural enemies were fluctuate. The density of the pest was quite high in the control plot, while the natural enemy density was high enough in the application plots of Mindi, Mahogany, and Soursop extracts.

Testing the capability of spectral resolution of the new multispectral sensors on detecting the severity of grey leaf spot disease in maize crop

In this study, we tested whether GLS field symptoms on maize can be detected using hyperspectral data re-sampled to WorldView-2, Quickbird, RapidEye and Sentinel-2 resolutions. To achieve this objective, Random Forest algorithm was used to classify the 2013 re-sampled spectra to represent the three identified disease severity categories. Results showed that Sentinel-2, with 13 spectral bands, achieved the highest overall accuracy and kappa value of 84% and 0.76, respectively, while the WorldView-2, with eight spectral bands, yielded the second highest overall accuracy and kappa value of 82% and 0.73, respectively. Results also showed that the 705 and 710 nm red edge bands were the most valuable in detecting the GLS for Sentinel-2 and RapidEye, respectively. On the re-sampled WorldView 2 and Quickbird sensor resolutions, the respective 608 and 660 nm in the yellow and red bands were identified as the most valuable for discriminating all categories of infection.

Applying the generalized additive main effects and multiplicative interaction model to analysis of maize genotypes resistant to grey leaf spot

SUMMARYAnalysing the stability and adaptation of cultivars to different environments is always necessary before recommending them for planting on large areas. Additive main effects and multiplicative interaction (AMMI) models have been used to analyse genotype-by-environment interactions (G × E). AMMI models require data with homogeneous variance, normal errors and additive effects. However, agronomic data do not always conform to these statistical assumptions. The objective of the present study was to analyse G × E interactions for severity and incidence of grey leaf spot, a foliar disease in maize caused by Cercospora zeae-maydis, using a generalized AMMI model. Data were collected and evaluated for 36 maize cultivars from experiments carried out in nine Brazilian regions in 2010/11 by the Empresa Brasileira de Pesquisa Agropecuária (EMBRAPA – Milho e Sorgo). Only two of three stable genotypes defined by a quasi-likelihood model with a logistic link function could be recommended for their desirable agronomic characteristics. Four growing locations in which the genotypes were stable were identified, but in only one of these was stability associated with very severe grey leaf spot disease. Cultivars adapted to specific locations with low percentage disease severity were also identified.

Response of groundnut (Arachis hypogaea L.) cultivars to late leaf spot disease (Passalora personata) under different sowing dates

Experiments were conducted to investigate the effect of date of sowing on groundnut cultivars against late leaf spot disease severity, defoliation, frequency and size of the leaf spot which revealed that all these aspects were significantly influenced by the date of sowing and crop varieties which directly affect the pod yield and test weight. The crop sown early on 25th June exhibited maximum mean late leaf spot disease severity (range 43.63 to 54.05%), defoliation (range, 17.22 to 22.30%), frequency (range, 1.32 to 1.78 / mm2) and size (range, 1.49 to 1.56 / mm2) and thereby gave reduced pod yield (range, 1225 to 1720 kg/ha) and test weight (28.66 to 32.97 g) followed by 10th July and 25th July. Among the groundnut cultivars, susceptible cv. JL 24 exhibited maximum mean disease severity (range, 35.94 to 54.05 %), defoliation (range, 11.61 to 22.30 %), frequency (range, 1.23 to 1.78 / mm2) and size (range, 1.26 to 1.56 / mm2), followed by TAG 24 and TG 26. However, LGN 1 exhibited least mean disease severity, defoliation, frequency and size with the highest pod yield (ranges, 1720 to 2332 kg/ha) and test weight (ranges, 32.97 to 38.59 g).

First report of tomato leaf spot caused by Fusarium proliferatum in China

A severe leaf spot disease was observed in a commercial tomato greenhouse in Dalian, Liaoning Province, China in January 2014. Typical symptoms included necrotic spots with dark brown, slightly sunken, irregular lesions on the leaves and stems, leading to wilting. The causative pathogen was identified as Fusarium proliferatum (Matsush.) Nirenberg on the basis of morphological characteristics and PCR amplification and sequence analysis of five genes, namely translation elongation factor-1α (TEF), β-tubulin (BT), fumonisin biosynthetic polyketide synthase (FUM1), histone H3 (H3) and calmodulin (Cal). Pathogenicity was confirmed by fulfilling Koch’s postulates. To our knowledge, this is the first report of leaf spot disease on tomato caused by F. proliferatum in China.